Commit 1104a885 authored by David Sterba's avatar David Sterba Committed by Chris Mason
Browse files

btrfs: enhance superblock checks 



The superblock checksum is not verified upon mount. <awkward silence>

Add that check and also reorder existing checks to a more logical
order.

Current mkfs.btrfs does not calculate the correct checksum of
super_block and thus a freshly created filesytem will fail to mount when
this patch is applied.

First transaction commit calculates correct superblock checksum and
saves it to disk.

Reproducer:
$ mfks.btrfs /dev/sda
$ mount /dev/sda /mnt
$ btrfs scrub start /mnt
$ sleep 5
$ btrfs scrub status /mnt
... super:2 ...

Signed-off-by: default avatarDavid Sterba <dsterba@suse.cz>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent b6919a58

fs/btrfs/ctree.h

+4 −2
Original line number Diff line number Diff line
@@ -2793,8 +2793,10 @@ BTRFS_SETGET_STACK_FUNCS(super_cache_generation, struct btrfs_super_block, 


static inline int btrfs_super_csum_size(struct btrfs_super_block *s)

{

	int t = btrfs_super_csum_type(s);

	BUG_ON(t >= ARRAY_SIZE(btrfs_csum_sizes));

	u16 t = btrfs_super_csum_type(s);

	/*

	 * csum type is validated at mount time

	 */

	return btrfs_csum_sizes[t];

}

fs/btrfs/disk-io.c

+67 −15
Original line number Diff line number Diff line
@@ -356,6 +356,44 @@ out: 
	return ret;

}



/*

 * Return 0 if the superblock checksum type matches the checksum value of that

 * algorithm. Pass the raw disk superblock data.

 */

static int btrfs_check_super_csum(char *raw_disk_sb)

{

	struct btrfs_super_block *disk_sb =

		(struct btrfs_super_block *)raw_disk_sb;

	u16 csum_type = btrfs_super_csum_type(disk_sb);

	int ret = 0;



	if (csum_type == BTRFS_CSUM_TYPE_CRC32) {

		u32 crc = ~(u32)0;

		const int csum_size = sizeof(crc);

		char result[csum_size];



		/*

		 * The super_block structure does not span the whole

		 * BTRFS_SUPER_INFO_SIZE range, we expect that the unused space

		 * is filled with zeros and is included in the checkum.

		 */

		crc = btrfs_csum_data(raw_disk_sb + BTRFS_CSUM_SIZE,

				crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);

		btrfs_csum_final(crc, result);



		if (memcmp(raw_disk_sb, result, csum_size))

			ret = 1;

	}



	if (csum_type >= ARRAY_SIZE(btrfs_csum_sizes)) {

		printk(KERN_ERR "btrfs: unsupported checksum algorithm %u\n",

				csum_type);

		ret = 1;

	}



	return ret;

}



/*

 * helper to read a given tree block, doing retries as required when

 * the checksums don't match and we have alternate mirrors to try.
@@ -2249,12 +2287,31 @@ int open_ctree(struct super_block *sb, 
		     fs_info, BTRFS_ROOT_TREE_OBJECTID);



	invalidate_bdev(fs_devices->latest_bdev);



	/*

	 * Read super block and check the signature bytes only

	 */

	bh = btrfs_read_dev_super(fs_devices->latest_bdev);

	if (!bh) {

		err = -EINVAL;

		goto fail_alloc;

	}



	/*

	 * We want to check superblock checksum, the type is stored inside.

	 * Pass the whole disk block of size BTRFS_SUPER_INFO_SIZE (4k).

	 */

	if (btrfs_check_super_csum(bh->b_data)) {

		printk(KERN_ERR "btrfs: superblock checksum mismatch\n");

		err = -EINVAL;

		goto fail_alloc;

	}



	/*

	 * super_copy is zeroed at allocation time and we never touch the

	 * following bytes up to INFO_SIZE, the checksum is calculated from

	 * the whole block of INFO_SIZE

	 */

	memcpy(fs_info->super_copy, bh->b_data, sizeof(*fs_info->super_copy));

	memcpy(fs_info->super_for_commit, fs_info->super_copy,

	       sizeof(*fs_info->super_for_commit));
@@ -2262,6 +2319,13 @@ int open_ctree(struct super_block *sb, 


	memcpy(fs_info->fsid, fs_info->super_copy->fsid, BTRFS_FSID_SIZE);



	ret = btrfs_check_super_valid(fs_info, sb->s_flags & MS_RDONLY);

	if (ret) {

		printk(KERN_ERR "btrfs: superblock contains fatal errors\n");

		err = -EINVAL;

		goto fail_alloc;

	}



	disk_super = fs_info->super_copy;

	if (!btrfs_super_root(disk_super))

		goto fail_alloc;
@@ -2270,13 +2334,6 @@ int open_ctree(struct super_block *sb, 
	if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_ERROR)

		set_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state);



	ret = btrfs_check_super_valid(fs_info, sb->s_flags & MS_RDONLY);

	if (ret) {

		printk(KERN_ERR "btrfs: superblock contains fatal errors\n");

		err = ret;

		goto fail_alloc;

	}



	/*

	 * run through our array of backup supers and setup

	 * our ring pointer to the oldest one
@@ -3561,14 +3618,9 @@ int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid) 
static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,

			      int read_only)

{

	if (btrfs_super_csum_type(fs_info->super_copy) >= ARRAY_SIZE(btrfs_csum_sizes)) {

		printk(KERN_ERR "btrfs: unsupported checksum algorithm\n");

		return -EINVAL;

	}



	if (read_only)

		return 0;



	/*

	 * Placeholder for checks

	 */

	return 0;

}

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